Injection foam molding system



Aug. 31, 1965 F. A. AXELSSON INJECTION FOAM MOLDING SYSTEM 4 Sheets-Sheet 1 Filed Sept. 20, 1963 INVENTOR. ram; 4. AXHJYOA/ BY Aug. 31, 1965 F. A AXELSSON INJECTION FOAM MOLDING SYSTEM 4 Sheets-Sheet 2 Filed Sept. 20, 1963 INVENTOR Fdlkf ,4. 4/553 BY %z% 1, 1965 F. A. AXELSSON 3,203,042

INJECTION FOAM MOLDING SYSTEM Filed Sept. 20, 1965 4 Sheets-Sheet 3 INVENTOR. FOAM. A AXZ $50M 1965 F. A. AXELSSON 3,203,042

INJECTION FOAM MOLDING SYSTEM Filed Sept. 20, 1963 4 Sheets-Sheet 4 30/ aoe 307 3/0 3/5 303 J/O If]. I I 5/2 INVENTOR $14? 4. XIII [A519 01/ BY I I United States Patent 3,203,042 INJECTION FOAM MOLDING SYSTEM Folke A. Axelsson, Grand Haven, Mich., assignor to Airspace, Inc., Fruitport, Mich., a corporation of Michigan Filed Sept. 20, 1963, Ser. No. 310,210 3'Claims. (Cl. 18-4) The invention relates to an injection molding system and apparatus, and to an injection molding method, and more particularly to mass production injection molding and handling apparatus for laminated panels having an expanded foam plastic core.

Since foamed materials of plastics exhibit excellent thermal insulation qualities, such materials possess excellent potential as a fill in structural walls, panels and the like. Consequently, it is known to foam in situ plastic foam between Walls for insulation. This procedure employs low pressure foaming materials and methods, resulting in a relatively high density material, usually in the range of about five pounds per cubic foot.

It has been determined, however, that high pressure foaming between sheets of material such as metal, plywood, Formica, Micarta or the like produces a resulting sandwich having a desirable low density and a superior structural strength. Low density means better insulation and less material cost. The sheet material enclosing the laminated panel need only be thin, and can actually be highly flexible before lamination. The resulting laminated panel from these sheets and a stiff foam has excellent rigidity as well as high thermal insulating qualities.

for this is because of difiiculties involved with the large initial pressure, exerted by the high pressure foaming material, during chemical reaction and the subsequent lesser but still substantial pressures which vary from the initial start of reaction to the final stages of curing. These factors result in the difiiculty of maintaining the desired product configuration and dimensional tolerances while the structure is undergoing the high internal pressures. This has presented a very substantial problem heretofore from a production standpoint.

Methods suggested to overcome it include the use of a large high pressure molding press to retain the entire structure during both the reaction period and also the curing period. This is often about one-half to threequarters of an hour. At this slow rate of production, however, due to the tie-up of the expensive pressure equipment, the over-all economics of fabrication are so poor that the foam panels cannot begin to compete with those of competitive materials.

Injection molding offers an excellent potential for mass production of foam core sandwiches. To form sandwiches by this method, however, requires expensive pressure restraining equipment to retain the panel against bulging. Each panel must be restrained, moreover, for a considerable period of time, often around one half hour, until curing occurs. In addition, a mixing and injection head is necessary to inject the reagents into the molds restrained in the press. This head is also expensive and is idle most of the actual production time.

It is therefore an object of this invention to provide an economical injection molding apparatus for forming high-pressure foam-core laminated sandwiches.

It is another object of this invention to provide a method and apparatus of forming laminated, high pressure, foam core, panel-type sandwiches capable of mass production in a highly eflicient, competitive and economical manner.

It is still another object of this invention to provide apparatus for forming foam core panel type sandwiches, using high pressure foam injection molding, retaining the dimensional tolerances and desired configuration of the article, yet to do so in a manner allowing the formation of panels repeatedly on a rapid production basis.

Another object of this invention is to provide pressure injection, mass production apparatus for forming foamed core laminates on an economical, efiicient basis. The most effective use is made of all components, including the mixing and injection head which has a short use period per panel, and the pressing equipment which has a long use period per panel.

These and other objects of this invention will become apparent upon studying the following specification in conjunction with the drawings in which:

FIG. 1 is a plan diagrammatic view of the novel system and apparatus;

FIG. 2 is a plan diagrammatic view of the novel system and apparatus arranged in generally radial fashion around a common injection head;

FIG. 3 is a perspective view illustrating one of the production line setups of the apparatus;

FIG. 4 is a perspective view illustrating one of the stationary pressure retention zones of one of the lines of the apparatus;

FIG. 5 is a fragmentary perspective view of an elevator in one of the lines of the apparatus;

FIG. 6 is a perspective exploded view of one of the mold assemblies on a conveyorized car;

FIG. 7 is a sectional view of the assembled mold on the car illustrated in FIG. 6;

FIG. 8 is a sectional view of the completed foam core, laminated product formed with this apparatus; and

FIG. 9 is a fragmentary sectional view of one end of the stationary retention means of the press.

Referring now specifically to the drawings, the apparatus as illustrated in FIG. 1 includes a common mixing and injector head 12, chemical reactant pressure vessels 14 (illustrated diagrammatically), and a plurality, here two, of high pressure molding production lines 16 and 18.

In FIG. 2, the injection head 12 accommodates a plurality of generally radially oriented production lines 16a, 16b, 16c and 16d. These are representative of the multiple line-single injection head combination and system used to advantage with the invention.

The variations shown in FIGS. 1 and 2 are illustrative of the novel system which can assume any of several additional variations not specifically shown. These two illustrate the novel principles and combination so that, in view of the teachings herein, the others would be apparent to those skilled in the art. Further drawings would therefore be redundant.

The reagent mixing and injection head is of known construction and may be purchased on the open market. It is designed to receive the separate reagents from pressure vessels 400, 402, 404 and 406 when the valves to these are opened using suitable manual push button controls 410 on the front of the head. The head communicates with the pressure vessels by flexible tubes 408. This equipment can be purchased on the market.

The head is mounted in a central position adjacent the stationary pressure retention zones 20 (to be specifically described hereinafter) at the injection end of each and every production line of the system. The head is no mally suspended on an overhead support beam of any suitable type such as a ceiling beam with a hoist. Its suspension element 412 (FIG. 4) enables it to be swiveled or rotated to allow an operator to operate the push button control panel from a position adjacent each high pressure retention zone 20 where the reagents are injected into the mold by the operator.

A common outlet for the mixed reagents is located at the bottom of the mixing head. A flexible tube 314 is attached to the head in communication with the outlet opening. The tube can be readily flexed to any one of the several molds in the respective injection zones to inject the mixed but unreacted chemicals into the selected mold. The tube is unreactive with the chemicals. It is preferably of a transparent or at least a translucent material such as Tygon to allow visual observation and control of injection.

Each of the production lines has its injection zone 20 immediately adjacent the head to enable the mixed reagents to be immediately injected into the molds after passing a short distance through the tube. The chemical reaction begins very slightly almost immediately upon mixing in the head, and proceeds exponentially since it is usually exothermic and self-propagating once started. Any delay in injection into the pressurized mold could cause premature reaction and pressurization due to the extensive expansion occuring with foaming. Also, any premature increase in temperature of reagents due t friction, if passed through a long tube, could cause uncontrolled expansion.

The number of production lines employed with the common injection head will vary depending upon the pressure retention period required during reaction and curing. For example, with a stiff polymethane foam mechanically expanded with a gas, such as Freon, the mold must be retained against maximum expansion pressures of about 80,000 p.s.i. for about 4-5 minutes, and then against maximum curing pressures of about 30,000 p.s.i. for about 25-30 minutes. Other materials require different restraint time periods. Since the injection time is only about 1 minute or so, a large number of lines are arranged radiating away from the common head.

The apparatus is especially suitable for the high pressure formation of panel-type laminated sandwiches having a low density, foamed plastic core of rigid or stiff foam plastic, and a pair of overlying sheet elements. The sheets may be of sheet metal such as steel, aluminum, or etched stainless steel, or of Formica, Masonite or other suitable metallic materials, pressed fibrous materials or synthetics. The particular sheet material is not critical.

The completed laminates are normally of a thickness of one to three inches, for example, and may be rectangular in cross section, generally 'flat, or alternatively, formed to particular curvatures and configurations. For purposes of convenience, the inventive apparatus will be descnbed with respect to a rectangular panel which is flat. The average such panel is several feet in width, e.g. about four feet and several feet in length, eg. about eight feet. These, of course, are only representative dimensions and configuration features for illustrative purposes.

Each of the production lines of the plurality employed comprises an elongated conveyorized line including several distinct portions. Each comprises a stationary, pressure restraining or retaining means 20, an adjacent elevator 22, an elongated conveyor 24 including two sets of conveyor tracks one above the other, and adapted to convey the movable mold-retaining cars 26, a second elevator 28 at the opposite end of the line, and a supplemental hoist 30 for disassembling and reassembling the restraining means and mold of the mold cars.

Each of these conveyor lines supports several of the cars 26. For purposes of convenience, only one car is shown in detail. The mobile cars 26 move along the tracks into and out of restraining means 20 on the upper 4 and lower tracks. A two stage restraining means is employed for the mold, with the car itself forming a mobile restraining means for the curing article in the mold, and the stationary restraining means 20 being a reinforcing, temporary retainer for the individual cars during the initial chemical reaction of the foaming plastic. The conveyor system also extends directly into the stationary restraining means 20 and enables the individual mobile restraining means or cars to move into and out of the temporary restraining means for initial reaction therein and subsequent curing on other portions of the conveyor.

Each of the individual cars 26 includes a base 40 (FIG. 6 and FIG. 3), and an attached pressure cover hold-down element 42 held in a spaced relationship from base 40 by a plurality of upright spacers 44 on opposite sides of the car. The hold-down is clamped tightly to the base against these spacers in this particular spaced relationship by clamping means. The clamping means as shown comprises a plurality of flanges on opposite sides of cover 42, a plurality of flanges 48 on the opposite sides of base 40, and threaded tie bars 50 (FIG. 3) extending therebetween.

Both the bed and the pressure cover of this restraining means are basically rectangular frames formed of metal stock such as steel. The periphery of the construction is interconnected by weldment to a plurality of parallel, spaced steel ribs 54. The base and cover are both rigid and sturdy, so that when clamped together on the edges, they are capable of retaining the inter-mediate mold as- :sembly against pressure of up to about 30,000 p.s.i.

The bed of each car is covered by an element 58 forming a continuous surface. Typically, t is a plywood sheet of substantial thickness forming a continuous bed surface for the mold. Preferably, this is covered with a metal sheet of aluminum for better release. The lateral sides of the mold are defined by a pair of uprights such as angle irons 60 and 62 (-FIG. 6) secured to mold board 58. The mold also includes front and back fixed bar elements 66 and 68. The four upright surfaces therefore define an elongated chamber there'between. Preferably, a removable bar 70 is spaced from fixed bar 68 by a plurality of short horizontal spacer blocks or tubes 72 for easier disassembly of the mold.

To achieve simplified assembly and disassembly, and to provide an offset on one side of the molded article, one side of the mold includes an elongated rod 76 of rectangular cross section extending along the inner face of angle iron 62. A stepped plate 78 is abutted against and fits over the bar in the mold. The other side includes a pair of angle bars 80 and 82, the specific function of which will be described hereinafter. All of these insert elements are especially suited to the particular edge construction of the panel illustrated. These may be modified, eliminated, or supplemented to achieve other panel edge configurations or junctures.

The mold is enclosed on the top by a second mold board '86, ordinarily of plywood of a substantial thickness. Thus, the two mold boards 58 and 86, and the peripheral elements 60, 70, 62 and 66 define a generally rectangular, substantially flat chamber a few inches in height and several square feet in area for molding.

Normally, the upper mold board 86 is loosely suspended from the upper or cover restraining frame 42 as by a pair of chains 90 on the forward and rearward ends. This enables hoisting of the upper mold board with the restraining cover 42 for disassembly and reassembly with maximum ease and speed.

The upper restraining element 42 includes a generally inverted U-shaped hoist bracket 98 on top for cooperation with the hook 100 of a conventional hoist 102. This hoist may be mounted on a suitable I beam track 104 which extends longitudinally of the conveyor. The track is mounted to overhead support 106 which, being of inverted U-shaped configuration, includes a cross beam and a pair of spaced support legs extending downwardly on opposite sides of the production line conveyor.

The bed of the restraining car has a plurality of at least four depending roller wheels 110 mounted fore and aft on brackets 112 to the bottom and side edges of the car. These rollers are configurated with a peripheral groove to interfit with the pair of upper tracks 116 and 118 or with the pair of lower tracks 120 and 122 (FIGS. 3 and 5). i

The stationary restraining means 20 includes a fixed upper frame and a vertically shiftable lower frame. Each of these frames in essence comprises a jaw of a vertical restraining means. The upper jaw is formed by a series of spaced, adjacent, elongated, parallel, I-beams 140 welded to and suspended from a pair of overhead, generally inverted, U-shaped mounts 142 and 144. These mounts are supported on suitable interconected I beams or the equivalent 146 attached to the floor. The lower jaw of this restraining means likewise is formed of a plurality of spaced, parallel I-beams 150. These are attached to a pair of spaced underlying transverse supports 152 and 154. These are interconnected by cross ties 155.

The ends of these transverse supports interfit in the vertical slots 156 (FIG. 9) of the I beams forming the vertical legs of supports 142 and 144. The opposite ends of transverse beams 152 and 154 are therefore guided during vertical reciprocal movement. Mounted under each of these beams 152 and 154 is a pair of fluid cylinders. Thus, fluid cylinders 160 and 162 hoist and lower beam 152, while cylinders 164 and another (not shown) simultaneously hoist beam 154. These move the upper surface of I-beams 150 (forming the lower jaw) to positions above and below the level of the conveyor tracks extending into the restraining means. Only one set (here the upper set) of conveyor tracks 116 and 118 extend into the restraining means between the two jaws.

The upward movement of the lower jaw is limited by spacers 170 (FIG. 9) .placed in the channels of the I beam vertical support legs. Their upper ends abut the cross members of support 142 or 144, and the lower ends abut beams 152 and 154. For these reasons, the initial compression actually applied to the movable restraining car and its mold is just sufficient to place all parts in tight relationship and to grip the car firmly. The compression i definitely limited by the spacers. The cylinders provide a large reaction force against any tendency of the car to expand under pressure of the reacting chemicals during foaming. Consequently, it will be seen that the compression restraining means, in both its stages, provides reaction pressure or restraint against any tendency of the mold to expand, and only applies a forceable compressive action on the mold other than this reaction force. This is true of the car because of spacers 44 (FIGS. 3, 6 and 7) which enable the upper and lower car restraining elements to force the components into proper tight engagement and interfit and grip the mold, but not to excessively compress it. It is true with respect to this fixed or stationary restraining means 20 because of the plurality of spacers 170.

The ends of tracks 116 and 118 may be suitably vertically supported by legs 190 as necessary, and may be interconnected by a cross piece 192. The remainder of the upper tracks 116 and 118 is mounted upon and supported by a plurality of spaced brackets 119 and 121. The lower tracks are also atfixed to these brackets to maintain their parellel aligned relationship. Also, a suit able car step 194 is provided on the lower bed of the stationary restraining means to prevent a car being wheeled into the restraining means from going too far.

The hydraulic cylinders 160 and 162 are capable of restraining large forces such as pressures of 80,000 p.s.i. on a panel several square feet in area. Conceivably, the cylinders may be substituted by equivalent mechanical restraining means capable of being moved from a lowered condition to an elevated position adjacent the car. Also, within the broader aspects of this invention, the upper jaw may move instead of the lower jaw. However, it is preferable to shift the lower jaw upwardly since this elevates the car above its track, thereby removing the wheels from the track as illustrated in FIG. 3. This eliminates the possibility of the application of pressure between the wheels and tracks. Thus, the upper surface of the lower I-beams 150 are purposely shifted from a position below these tracks, to a position above the tracks in the restraining condition.

In the preferred form of the apparatus, a track type element (FIG. 5) 22 is located adjacent the stationary restraining means and in alignment with the conveyor tracks between the jaws. This elevator includes an overhead, inverted, generally U-shaped support 200 anchored on its lower ends. Its cross beam extends across and above the elevator tracks. Mounted beneath and to this cross beam is a conventional power hoist 202. To the hook 204 of the hoist is attached a cross beam 206. Suspended from this beam are two pairs of spaced diagonal supports 20S and 210. To the ends of these diagonal supports are mounted elevator track sections 116' and 118'. These track sections, when raised, form a part of the upper tracks 116 and 118, and when lowered, form a part of the lower tracks 120 and 122. The track sections are suitably interconnected by cross braces 216 to retain their alignment with these upper and lower tracks. Vertical supports 220 extending from beam 206 down to track sections 116' and 118 are interfitted in the grooves of the I beams forming the vertical legs of the U-shaped support 200. Thus, the elevator is guided vertically during its lowering and raising.

A second elevator 28 also like elevator 22 illustrated in FIG. 5, is provided at the opposite end of the conveyor line. The elevator 28 thus includes an inverted generally U-shaped overhead support 240, a hoist 242 suspended therefrom (FIG. 3) and track sections like those illustrated in FIG. 5.

Adjacent the second elevator 28 is an unloading and reassembly station 30. This station (FIG. 6) as described previously, includes support 106, hoist track 104, and hoist 102, to disassemble and reassemble the components of the mobile cars.

When each of the mold cars is assembled, it assumes the form illustrated in FIG. 7. The restraining base 40 on wheels 110 has attached thereto, vertically spaced thereabove, the upper pressure retainer cover 42. As explained previously, these are spaced by upright spacers 44 at the opposite sides of the elements, and are secured together by tie bolts 50 extending between flanges 46 and 48. Supported on and attached to the cross ribs of bottom 40 is the mold board 58. Attached to this mold board are the side angle irons 60 and 62 as well as end elements 66 and 68 (FIG. 6). The lower sheet metal or equivalent layer 300 forming the bottom of the finished panel is supported on this mold board 58,

and retained within the confines of the mold assembly against bar 76 and offset Z-shaped element 78 on one side, and against inverted, L-shaped elements 80 and 8-2 on the opposite side. The ends of the panel are retained between fixed bar 66 and removable bar 70. The upper layer 302 which forms the opposite skin of the completed panel (FIG. 8) 310 is held in a spaced parallel relationship to bottom layer 300. Its hooked flange 306 which is turned downwardly, hooks over the upwardly extendin plate 78. It also rests upon end members 66 and 70. Its opposite side from flange 306 is abutted against plate 82. The top mold board 86 rests upon this upper layer. The completed assembly is not compressed excessively, but is merely retained in tightly engaged, sealed relationship to define an internal cavity 308 into which foam 312 (FIG. 8) is later injected. It is injected with flexible tube 314 (FIGS. 7 and 4) which extends into 7 opening 318 (FIG. 6) in the side of each mold assembly to communicate with chamber 308.

Operation To efficiently mass produce the high pressure, low density, stiff foam panels as those illustrated in FIG; 8, the following sequence is performed.

Several like production lines are assembled, with the stationary pressure retention zone of each being adjacent the common injection head. A plurality of like mold cars are used on each conveyor line. To begin the process, the first mold car on each line is assembled at station 30 on upper tracks 116 and 118 Each includes the elements illustrated in exploded form in FIG. 6 in the manner illustrated in the assembled form in FIG. 7. Bar '76 is abutted against the inside face of angle iron 62, and offset plate 78 is rested upon and abutted against this bar so that its upper flange extends upwardly above angle iron 62. Then inverted L-shaped bar 80 is positioned against and on top of L-shaped bracket 60 on the opposite side of the mold. The lower metal sheet 300 is then inserted inside the mold to rest upon the bottom mold board 58. It abuts against plate 78 on one side, and the L-shaped bracket 80 on the opposite side. Then the second L-shaped bracket 82 is inserted so that its lower end abuts and holds down the upwardly projecting flange on lower layer 300. The upper article sheet is then mounted so that its downwardly turned flange 306 fits over the top edge of element 78, and the opposite side abuts against L-shaped bracket 82. Then the top rnold board 86 is lowered, along with top frame 42 of the mobile restraining means. Tie bolts 50 are then tightened between the mounting flanges on the sides to cause upper frame element 42 to be tightly held down on spacers 44. The unit is then ready for movement down the conveyor tracks 116 and 118 across the elevated conveyor track sections 116' and 118' of elevator 22, and into temporary restraining means 20.

This same process is also achieved by workers on cars on each of the other production lines in a sequential fashion with intervals of a minute or so between each line.

As the first car moves into the confines of the first restraining means, the lower jaw must be in a lowered condition so as not to interfere with the entry of the car. The car moves in until it abuts stop flange 194 (FIG. 4). Then cylinders 160, 162 and 164 or their equivalent, are actuated to elevate the lower jaw of the restraining means and hoist the first car and mold off the conveyor tracks as illustrated in FIG. 3. When the mechanism has been hoisted sufficiently to just abut the top of the car against I-beams 140, spacer elements 170 abut supports 142 and 144 and beams 152 and 154 (FIGS. 9 and 4). The unit is now ready to be injection molded.

The individual chemical reagents for forming the selected foam plastic are retained separate in suitable pressure vessels 14. As an example, when using an expanded polyurethane foam, a polyether resin, a isocyanate, a catalyst, and the pressurized gaseous expanding agent are maintained in pressure tanks 400, 402, 404 and 406. These are all simultaneously injected in the necessary quantity relationships through flexible hoses 408 into the mixing and injection head. The flexible hose 314 is inserted through an opening into the first mold of the first car and the ejection head is. actuated to cause the mixed unreacted reagents to be injected into molding space 308 (FIG. 7) to fill it. The hose is flexed in an arc inside the mold to obtain uniform distribution of the reagents.

An initial time lag is caused by delayed reaction of the chemical reagents to enable fill before significant pres sure reaction. This is achieved in well-known fashion either by controlling the temperature of one or more of the reagents, or by the selection of reagents, or both.

Thus, the operator has adequate time to fill the space and insert a plug in the opening before reaction begins to any considerable extent. Filling takes about a minute, more or less. A suitable plug is then inserted in the filling opening.

Immediately after the injection head operator has the first mold filled and the hose retracted, he causes it to be rinsed by flushing it with a solvent such as methylene chloride, and flexes the hose in another direction to fill an adjacent mold on an adjacent line. The same filling process is repeated for the molds in each line restrained in the stationary restraint zones. Each filled mold and car remains in the restraint zone until the initial reaction pressure surge decreases substantially.

As the chemical reagents initially react and expand, extremely high internal pressures are created. For example, with high pressure polyurethane foaming, pressures in the neighborhood of 80,000 p.s.i. are experienced. The double restraining means of the mobile car restraining means and the stationary restraining means are suflicient to prevent expansion of the mold outside of its initial confines. Consequently, close dimensional tolerances are maintained in spite of these extremely high pressure-s. After the first few minutes of reaction, for example, about four minutes when reacting a rigid polyurethane foam, the initial reacting and expansion pressures in the neighborhood of 80,000 p.s.i. decrease to significantly lower values around 30,000 p.s.i. During the next half hour or so, the pressures slowly subside as the foam precures to its first solidified state.

Consequently, the stationary restraining means is purposely expanded and opened after the first few minutes to allow the car to be removed. The structure of the car itself, and more specifically, its restraining means, maintains the panel in it dimensionally accurate tolerances during the lower pressure curing portion of the cycle.

The car is then pushed out onto track sections 116' and 118' of elevator 22. The elevator is lowered to move the car with its curing charge to lower tracks 120 and 122. The car is then pushed onto the lower tracks and slowly advanced, with several other like cars in various curing stages, to the opposite end of the line. The elevator 22 is then raised again and the next assembled car to be injection molded is advanced into the stationary restraining means. In the meantime, cars with laminates cured to the solid state, having reached the opposite end of the conveyor line, are hoisted from the lower conveyor tracks to the upper conveyor tracks by elevator 28. It then is shifted into the unloading and reassembly station 30.

At this station, tie bolts 50 are removed and the assembly is taken apart to break loose the finished, sandwich, panel-type unit. The panel has cured to a self-sustaining state. It actually requires several additional hours, e.g., 48 or so, for the chemical curing reaction to reach its final fully cured state, but during this time, after the initial pre-cure, it does not exert any significant outward pressure. The mold is then cleaned a little bit as necessary, is reassembled, and is advanced on down to the stationary restraining means again.

Just after this first car with its mold is removed from the first restraining means, the adjacent car and mold in the adjacent line has reacted sufliciently to be removed from its restraining means. It then goes through the same sequence of events as that just described.

The third car and mold is then treated likewise, and so forth through the plurality of production lines. Consequently, the plurality of cars and molds on each line form a circuit of recirculating cars in various stages of mold preparation, filling, expansion and double restraint, curing, unloading and mold reassembly, while each circuit is sequential to the adjacent one. All, therefore, employ the single mixing and inject-ion head in an extremely eflicient manner. This process is shown diagrammatically in FIG. 2, using only one car on each line for purposes of convenience. While car 26a is just leaving zone 20a after being filled and initially reacted, car 26b is being filled by hose 314 in zone 200. Car 26b with a curing charge is slowly moving along the lower tracks of line 16b to the far elevator 28b, and car 26d is being disassembled at unloading zone 30d for removal of the precured laminate and reassembly of the mold and car.

Each of the resulting laminated panels 310 has means to interfit with adjacent like panels for rapid, simple, tight assembly. The flange 306 along one edge of each panel is integral with skin 302, extends upwardly normal thereto to form leg 301, is bent down back upon leg 301 to form leg 303 which extend-s down part away along leg 301, and then is bent back up between legs 301 and 303 to form an inner catch hook. This receives and hooks the downwardly extending short leg 305 of upwardly extending flange leg 307 on the opposite side of the adjacent panel 310. The edges of the foam is stepped so that the lower protrusion 311 of panel 310 interfits with the lower recess 313 of panel 310, and the upper recess 315 of panel 310' receives the upper protrusion 317 of panel 310. The panels are therefore slid together and interlocked in a sealed manner.

It has been found that by utilizing this unique apparatus the foamed core units can be economically injection molded by the high pressure method under high production conditions, while still accurately maintaining the dimensional tolerances necessary. This enables, for the first time as far .as is known, the economical fabrication of such panels for use in mobile homes, animal housing, prefabricated housing, and many other uses.

Various additional advantages of .the apparatus and concepts set forth herein will occur to those in the art upon studying this foregoing preferred form of the invention. Also, it is conceivable that various minor structural modifications can be made in the particular details of construction specifically taught, while still employing the inventive concepts of the invention. Consequently, this invention is not to be limited merely to the particular structure shown, but only by the scope of the appended claims and the reasonably equivalent structures to those defined therein.

Iclaim:

1. An injection molding system for mass production of foam core sandwiches comprising: a mixing and injection head; a plurality of production lines arranged about said head for cooperation therewith; each of said lines having a plurality of mold cars, each having an internal mold restrained against expansion for containing foam sandwiches to be formed by injection molding; each line having elongated conveyor means operably engaged with and supporting a plurality of said cars for movement of said car-s therealong, enabling said cars :to be in diiferent zones thereof during various stages of injection, reaction, curing and unloading of the foam core sandwich; said cars each having support means retaining a pair of sheet panels in spaced relationship, and compression retention means holding said panels against expansion upon the injection of pressure foaming material between said panels; said compression retention means being releasable after curing of the foam core in said sandwiches for removal of said sandwich; a shiftable high pressure press at the injection and reaction zone of said conveyor means, including a bed beneath said car and an overhead pressure element, and means holding said bed and pressure element in fixed spaced relationship with each other and in contact with the car during injection and initial reaction of the foaming polymer to prevent expansion of said sandwich with generated pressures greater than the retention force of said compression retention means; each of said high pressure presses being adjacent said mixing and injection head; said head having an outlet conduit extending therefrom and communicable with the molds in the cars in said presses in sequential fashion, whereby said molds are filled, removed from said presses, cured, unloaded, and reassembled in sequential fashion between production lines.

2. The system in claim 1 wherein each of said cars in cludes rolling elements, and each of said conveyor means comprises tracks extending into its respective press and supporting the rolling cars; each of the cars comprising releasably interconnected upper and lower frame elements straddling a pressure mold and having spacer means therebetween to limit compression.

3. The system in claim 2 wherein said upper jaw is fixed and said lower jaw is shiftable toward said upper jaw to hoist said cars off said tracks during foaming reaction.

References Cited by the Examiner UNITED STATES PATENTS 1,958,422 5/34 Dinzl 18--4 2,027,165 1/36 Grubman 18-4 2,854,691 10/58 Strong 185 2,943,353 7/60 Fraul-a et .al. 18-4 XR 2,980,955 4/6'1 Sanko 185 3,040,381 6/62 P-ioch 18--4 XR 3,042,967 7/ 62 Edberg 184 XR 3,044,112 7/62 Perry l85 WILLIAM J. STEPHENSON, Primary Examiner. 

1. AN INJECTION MOLDING SYSTEM FOR MASS PRODUCTION OF FOAM CORE SANDWICHES COMPRISING: A MIXING AND INJECTION HEAD; A PLURALITY OF PRODUCTION LINES ARRANGED ABOUT SAID HEAD FOR COOPERATION THEREWITH; EACH OF SAID LINES HAVING A PLURALITY OF MOLD CARS, EACH HAVING AN INTERNAL MOLD RESTRAINED AGAINST EXPANSION FOR CONTAINING FORM SANDWICHES TO BE FORMED BY INJECTION MOLDING; EACH LINE HAVING ELONGATED CONVEYOR MEANS OPERABLY ENGAGED WITH SAID SUPPORTING A PLURALITY OF SAID CARS FOR MOVEMENT OF SAID CARS THEREALONG, ENABLYING SAID CARS TO BE IN DIFFERENT ZONES THEREOF DURING VARIOUS STAGES OF INJECTION, REACTION, CURING AND UNLOADING OF THE FOAM CORE SANDWICH; SAID CARS EACH HAVING SUPPORT MEANS RETAINING A PAIR OF SHEET PANELS IN SPACED RELATIONSHIP, AND COMPRESSION RETENTION MEANS HOLDING SAID PANELS AGAINST EXPANSION UPON THE INJECTION OF PRESSURE FOAMING MATERIAL BETWEEN SAID PANELS; SAID COMPRESSION RETENTION MEANS BEING RELEASABLE AFTER CURING OF THE FOAM CORE IN SAID SANDWICHES FOR REMOVAL OF SAID SANDWICH; A SHIFTABLE HIGH PRESSUER PRESS AT THE INJECTION AND REACTION ZONE OF SAID CONVEYOR MEANS, INCLUDING A BED BENEATHE SAID CAR AND AN OVERHEAD PRESSURE ELEMENT, AND MEANS HOLDING SAID BEAD AND PRESSURE ELEMENT IN FIXED SPACED RELATIONSHIP WITH EACH OTHER AND IN CONTACT WITH THE CAR DURING INJECTION INITIAL REACTION OF THE FOAMING POLYMER TO PREVENT EXPANSION OF SAID SANDWICH WITH GENERATED PRESSURES GREATER THAN THE RETENTION FORCE OF SAID CPMPRESSION RETENTION MEANS; EACH OF SAID HIGH PRESSURE PRESSES BEING ADJACENT SAID MIXING AND INJECTION HEAD; SAID HEAD HAVING AN OUTLET CONDUIT EXTENDING THEREFROM AND COMMUNICABLE WITH THE MOLDS IN THE CARS IN SAID PRESSES IN SEQUENTIAL FASHION, WHEREBY SAID MOLDS ARE FILLED, REMOVED FROM SAID PRESSES, CURED UNLOADED, AND REASSEMBLED IN SEQUENTIAL FASHION BETWEEN PRODUCTION LINES. 